However, when the motor inertia is larger than the load inertia, the electric motor will require more power than is otherwise necessary for the particular application. This improves costs because it requires spending more for a engine that’s larger than necessary, and because the increased power intake requires higher working costs. The solution is by using a gearhead to match the inertia of the electric motor to the inertia of the strain.
Recall that inertia is a measure of an object’s resistance to improve in its movement and is a function of the object’s mass and form. The greater an object’s inertia, the more torque is needed to accelerate or decelerate the thing. This implies that when the load inertia is much bigger than the electric motor inertia, sometimes it can cause extreme overshoot or boost settling times. Both circumstances can decrease production range throughput.
Inertia Matching: Today’s servo motors are producing more torque relative to frame size. That’s because of dense copper windings, lightweight materials, and high-energy magnets. This creates higher inertial mismatches between servo motors and the loads they want to move. Utilizing a gearhead to better match the inertia of the motor to the inertia of the load allows for utilizing a smaller engine and results in a more responsive system that’s easier to tune. Again, this is accomplished through the gearhead’s ratio, where the reflected inertia of the load to the electric motor is decreased by 1/ratio^2.
As servo technology has evolved, with manufacturers generating smaller, yet better motors, gearheads have become increasingly essential partners in motion control. Finding the optimum pairing must take into account many engineering considerations.
So how will a gearhead start providing the power required by today’s more demanding applications? Well, that all goes back again to the fundamentals of gears and their capability to change the magnitude or path of an applied power.
The gears and number of teeth on each gear create a ratio. If a electric motor can generate 20 in-lbs. of torque, and a 10:1 ratio gearhead is mounted on its result, the resulting torque can be near to 200 in-lbs. With the servo gearhead ongoing focus on developing smaller footprints for motors and the gear that they drive, the ability to pair a smaller motor with a gearhead to achieve the desired torque result is invaluable.
A motor may be rated at 2,000 rpm, but your application may just require 50 rpm. Trying to run the motor at 50 rpm may not be optimal based on the following;
If you are working at an extremely low speed, such as 50 rpm, as well as your motor feedback quality isn’t high enough, the update price of the electronic drive could cause a velocity ripple in the application form. For instance, with a motor feedback resolution of just one 1,000 counts/rev you possess a measurable count at every 0.357 degree of shaft rotation. If the electronic drive you are employing to control the motor has a velocity loop of 0.125 milliseconds, it’ll search for that measurable count at every 0.0375 amount of shaft rotation at 50 rpm (300 deg/sec). When it generally does not see that count it’ll speed up the engine rotation to think it is. At the quickness that it finds another measurable count the rpm will become too fast for the application form and then the drive will sluggish the electric motor rpm back off to 50 rpm and then the whole process starts all over again. This constant increase and decrease in rpm is what will cause velocity ripple within an application.
A servo motor running at low rpm operates inefficiently. Eddy currents are loops of electric current that are induced within the electric motor during procedure. The eddy currents actually produce a drag pressure within the motor and will have a greater negative effect on motor functionality at lower rpms.
An off-the-shelf motor’s parameters might not be ideally suited to run at a low rpm. When an application runs the aforementioned engine at 50 rpm, essentially it is not using all of its obtainable rpm. As the voltage constant (V/Krpm) of the engine is set for a higher rpm, the torque continuous (Nm/amp), which is usually directly linked to it-can be lower than it needs to be. Because of this the application needs more current to drive it than if the application had a motor particularly designed for 50 rpm.
A gearheads ratio reduces the motor rpm, which is why gearheads are occasionally called gear reducers. Using a gearhead with a 40:1 ratio, the electric motor rpm at the input of the gearhead will end up being 2,000 rpm and the rpm at the result of the gearhead will become 50 rpm. Working the motor at the higher rpm will permit you to prevent the problems mentioned in bullets 1 and 2. For bullet 3, it allows the design to use much less torque and current from the electric motor based on the mechanical benefit of the gearhead.